This invention relates to a shadow-mask color picture particularly it relates to a shadow-mask color picture tube with reduced landing error.
Shadow-mask color picture tubes are used in most color television receivers. The shadow mask is a steel plate disposed behind the screen, perforated by a large number of small holes or slots. Beams from three electron guns are directed toward the shadow mask and pass through the perforations. The three beams that pass through a given perforation land on the screen in three different locations, which are provided with red, green, and blue phosphor coatings. Each beam thus produces a different color.
Shadow-mask color picture tubes are susceptible to a problem known as landing error, this being an error in the locations in which the beams land on the screen. If the landing error is such that a beam lands on a phosphor of the wrong color, the color purity of the image is impaired.
One of the causes of landing error is doming. This occurs when the shadow mask is heated by the impact of the electron beams and expands, the expansion causing the shadow mask to swell outward toward the screen in a dome-like shape.